Continuous catalyst conversion processes are common in the refining and petrochemical industry. The fluidized catalyst cracking of hydrocarbons is an important process for the production of lighter hydrocarbon components, and as such, it is an important process for the production of propylene. The fluidized catalytic cracking process continuously circulates a fluidized catalyst between a reactor and a regenerator.
Another route for the production of propylene can be obtained by the dehydrogenation of propane through catalytic dehydrogenation. The dehydrogenation catalysts generally comprise noble metal catalysts on acidic supports, such as alumina, or silica alumina, or zeolitic materials. However, the reaction is strongly endothermic, and requires a high temperature for the reaction to proceed at a satisfactory rate. At the same time, the reactions need to be controlled to limit the degradation of the propane to form methane and ethylene, and where the ethylene can be hydrogenated by the hydrogen released through the dehydrogenation of the propane. The process also leads to coking of the catalyst, and deactivates the catalyst. The catalyst therefore needs to be regenerated on a regular basis after relatively short periods of operation, or residence, in the dehydrogenation reactor.
The production of propylene through dehydrogenation is an endothermic process and requires a substantial amount of additional heating to allow the process to proceed. As a result, overall selectivity typically suffers due to temperature gradients across the catalyst bed. The hottest temperatures are desired at the outlet of the catalyst bed, but is not achievable with current state-of-the-art designs. Another problem is the excessive non-catalytic thermal residence time, due to the required heating of the feed prior to feeding into the reactor.